Circuit control plug



F'iled Dec. 50, 1947 Ihwentor JUL I A K I TMAN attorney latentecl Nov. 22, 1949 UNITED STATES PATENT OFFICE CIRCUIT CONTROL PLUG Julia Kitman, Pittsburgh, Pa. Application December 30, 1947, Serial No. 794,663

1 Claim. 1

This invention relates to an electric circuit control plug, and important objects and advantages thereof are to provide a control plug of the character described, which is designed and intended to supersede a fuse plug of the conventional type commonly used in branch circuits carrying the smaller currents, which will function automatically to break the circuit when the current strength reaches a predetermined value, which may be readily reset for repeated use Without removing same from the socket after having functioned to break the circuit, which is simple in its construction and arrangement, durable and efiicient in its use, positive in its action, and comparatively economical in its manufacture and use.

With the foregoin and other objects in view which will appear as the description proceeds, the invention resides in the construction, combination and arrangement of parts herein specifically described and illustrated in the accompanying drawing, but it is to be understood that changes in the form, proportions and details of construction may be resorted to that come within the scope of the claim hereunto appended.

In the drawing wherein like numerals of reference designate corresponding parts throughout the several views:

Figure 1 is a side elevational view, partly in cross section, of the improved electric circuit control plug, with the embodied control mechanism in the operative position.

Figure 2 is a similar view with the control mechanism in the inoperative position.

Figure 3 is a fragmentary side elevational view, partly in section, of the device, taken at right angles to the view shown in Figure 2.

Figure 4 is an enlarged side view of the associated contact members embodied in the present invention.

Referring in detail to the drawing, the improved electric circuit control plug comprises a hollow plug body I, including a top cover 2, which latter is fixed to the plug body by cementing or in any other suitable manner. The lower exterior portion of the plug body is surrounded by a fixed metallic threaded shell 3, and the bottom 4 of the plug body carries a fixed centrally disposed contact pin 5.

The plug body I and the top cover 2 are constructed of any suitable insulating material, and the assembly of the plug body and top cover, together with the embodied thread shell 3 and contact pin 5, provide a plug structure which has a general contour identical to the conventional type of fuse plug, and which is designed and intended to be screwed into the conventional type of electric socket.

A thermostatically controlled switch is mounted in the plug body I and comprises the horizontally aligned and opposed contact members, respectively indicated at 6 and I. The contact member 6 is fixed to the inner side of the upper free end portion of a bimetallic arm 8, which latter has its lower end secured by the contact pin 5.

The contact member I is carried at the inner end of a horizontally disposed contact rod 9. The contact rod is mounted for longitudinal shiftable movement in a supporting bracket Hi, which is secured to and depends from the top cover 2. The contact rod is provided with a head H at its outer end to limit the inward movement of the former in the supporting bracket. A comparatively light spiral spring I2 is mounted on the inner end portion of the contact rod between the contact member I and the supporting bracket. The spring l2 functions normally to hold the contact member I, carried by the contact rod 9, under constant pressure against the contact member ii, carried by the bimetallic arm 8.

A flexible conductor l3 connects the outer head ll of the contact rod 9 with the thread shell 3. It will here be noted that the conductor l3 may be constructed of material that will fuse to break the circuit when the current strength reaches a certain predetermined value.

A push button I4 is mounted in an openin 15 formed in the center of the top cover 2. A relatively strong spiral spring I6 is mounted in the opening l5 and surrounds and engages the push button. The action of the spring it normally tends to force the push button to its maximum position, as shown in Figure 2.

A rocker element I1 is pivotally supported, centrally of its length, by the supporting bracket In. One end of the rocker element extends loosely through an aperture l8 in an insulating plate IS. The other end of the rocker element extends loosely through an aperture provided therefor in a connecting leg 20, which latter is fixed to and depends from the lower end of the push button.

The insulating plate I9 is rectangularly-shaped and is vertically shiftable in a pair of opposed, vertically extending guide grooves 2| and in a horizontally extending groove 22. The grooves 2| are formed in the side wall of the plug body I and the upper ends thereof open into the horizontal groove 22 which is formed in the top cover 2. The insulating plate is over the contact members G and 'l, and when in the elevated position, as shown in Figure 1, the lower end thereof rests upon a squared seat 23, which latter is formed in the upper inner corner of the contact member 5. When in the lowered position, the insulating plate is disposed between the contact members 6 and 'l, as shown in Figure 2, and thereby prevents the contacting engagement of the members and l for the purpose to be described. The inner upper corners of the contact members are tapered, as respectively indicated at 24 and 25, to direct the insulating plate between the contact members when said insulating plate is shifting to the lowered position.

When the control mechanism of the improved control plug is in the operative position, as shown in Figure 1, the contact members 6 and I engage each other, and the insulating plate I!) is in the elevated position with the lower end thereof being seated under pressure in the seat 23 of the contact member 5. When the device is screwed into an electric socket in the manner of the conventional fuse plug, the circuit is completed through the contact pin 5, the bimetallic arm 8, the contact members (3 and 7, the contact rod 9, the head H, the conductor l3, and the threaded shell 3; Under normal conditions the contact members 6 and 1 always remain in contacting engagement with each other.

The construction and operation of the bimetallic arm 3 is such that if the current strength of the electric circuit reaches and exceeds the predetermined value, the bimetallic arm will be thermostatically actuated to shift the contact member s from its engagement with the contact member 2- whereby the circuit is broken.

s soon as the contact member 6 shifts to disengage the contact member I, the insulating plate is is released from the seat 23 and will snap to the lowered position between the contact members 6 and l, as shown in Figure 2, by the action of the spring I6. Upon return of the bimetallic arm 8 to the normal position, the contact member 6 cannot contact the contact member 7 due to the insulating plate is therebetween.

To again reclose the circuit, it will be necessary to manually depressthe push button !4, whereby the insulating plate I 9 will be shifted to the elevated position and again engaged in the seat 23 of the contact member 6, and allow the latter to engage the contact member I. By this arrang ment the circuit cannot be reclosed unless the device is manually reset in the manner stated.

The present invention provides a most efficient device of its kind, which may be economically employed for the purposes and in the manner herein set forth.

What I claim is:

An electric circuit control plug of the class described, comprising the combination of hollow plug body provided with vertically extending guide grooves and including a top cover, a thread shell surrounding the lower portion of said body, a contact pin fixed in the bottom of said body, a push button shiftably mounted in said cover, a supporting bracket secured to said cover and depending into said body, a horizontally disposed spring controlled contact rod provided with a head shiftably supported in said bracket, a thermostatically controlled vertically disposed bimetallic arm having its lower end secured by said pin, a pair of horizontally opposed contact members, one of said members being secured to the upper free end of said arm and the other of said members being secured to the adjacent end of said rod, a "(lb-1e conductor connecting said head with said shell, a vertically disposed insulating plate provided with an aperture shiftably engaged in said grooves, a connecting leg provided h an aperture carried by and depending from said push button, a rocker element pivot" supported by said bracket, one end of said ncnt ext-ending through the aperture in said plate and the other end of said element ext ndmg ough the aperture in said leg, and a s agin said push button, the normal action 01 aid spring tending to elevate ton and to force said plate between members, the manual depression of said pi button operating said element to elevate said plate and cause the contacting engagement of said members.

JULIA KITMAN.

CES CITEED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,373,128 Freese Mar. 29, 1921 1,732,295 Aichele Oct. 22, 1929 2,147,75-e Rivers Feb. 21, 1939 2,429,225 Grady Oct. 21, 1947 FOREIGN PATENTS Number Country Date 707,137 Germany June 14, 1941 

